1. Field of the Invention
The present invention relates to a fluid controlling method for controlling plural fluids, a microfluidic device using the fluid controlling method, and a process for fabricating the device.
2. Description of the Related Art
Such an attempt has been widely carried out that a micro flow channel is formed, in which two or more kinds of fluids (including liquid and gas) are flowed as being in contact with each other, and various chemical reactions (including synthesis and cleansing) are carried out an interface between them. As an example of the conventional microfluidic device, a micromixer using a coaxial flow channel has been known (as described, for example, in JP-A-2003-210959).
The micromixer has a flow channel in such a manner that one fluid A is coaxially surrounded by the other fluid B. Since the fluids A and B flow as laminar flows, the fluid A flowing at the center is not in contact with a wall of the flow channel, which brings about an advantage that particles contained in the fluid A do not stack on the wall surface.
Since two liquids form laminar flows in the micro flow channel, it is necessary to provide a certain structure for effectively agitating the liquids to promote the reaction between them. As an example of the conventional mixer device having an agitating structure, a device has been known which includes more than two zigzagged bars and mix two liquids by using a segment produced by a metal casting method (as described, for example, in U.S. Pat. No. 6,217,208).
A classifying device utilizing difference in specific weight or ascending force has been known (as described, for example, in JP-A-2001-276661 (paragraph (0004) and FIG. 4)).
In the classifying device, particles are introduced to a classifying area between upper and lower circular disks through an annular introducing slit, and air is made in fall from the outer circumference toward the center of the classifying area, whereby only particles having a particular particle diameter are classified to reach an annular slit provided in the lower disk, and thus the classified particles are taken out from a drawing duct.